In the prior art tumbler pin cylinder locks have been adapted to be changed for use with different keys. These kinds of locks have been particularly adaptable for hotels, apartments and office buildings where it is desirable to change the lock for use with a different key.
In these prior locks it was usually necessary to remove the cylinder from the door to make the changes and, in addition, tools were required to be inserted into the cylinders to make the key changes possible.
There have been other changeable locks which could be changed in place, but they also required a tool to be used from externally of the lock.
The present invention has eliminated the requirement for removal of the lock cylinders from the doors and, further, has eliminated the need for the use of an external tool.